Joint for high tension electric cables



Jan. 18, 1938.

J. K.IWEBB JOINTv FOR HIGH TENSION ELECTRIC CABLES Filed sept. ze, 19542 Sheets-Sheetl Jan. 18, 1938. "J, K, WEBB JOINT FOR HIGH TENSIONELECTRIC CABLES Filed Sept. 28, 1934 2 Sheets-Sheet 2 Patented Jan. 18,1938 I UNITED STATES PATENT OFFICE JOINT FOR HIGH TENSION ELECTRICCABLES John Krauss Webb, Aldwych, London, England, assigner to'International Standard Electric Corporation, New York, N. Y.

Application September 28, 1934, Serial No. 745,931 In Great BritainDecember 4, 1933 7 Claims. (Cl. 173-268) 'Ihis invention is forimprovements in or relatand the outer metallized paper being removed uping to joints for high tension electric cables. to the lead sheaths 2,2'. The lead sleeve 3 is The invention provides a method of jointingslipped over one cable end and the two cable cores high tension cableswhich comprises insulating 4, 4 are joined by means of the ferrule 5inthe 5 the joint with a liquid polymerizable material lusual manner.This ferrule may be of the hol- 5 free from volatile solvents, forexample an low or solid type according to whether a straight aromaticmono-olefine such as styrene, and through or barrier type of joint is tobe prothereafter polymerizing the material to form a vided. solidinsulation at the joint. The tapered insulation is preferably wiped l0The invention also provides a method of jointdown with a solution ofchlorinated diphenyl 10 ing oil impregnated paper insulated high tensionwhich assists the actual impregnating of the pacables which comprisesinsulating the joint with pers by the styrene at the subsequent fillinga liquid polymerizable material for example a stage, as it removes theoily barrier which othermixture of styrene and chlorinated aromatichywise might prove to be impenetrable by the illii drocarbon andthereafter polymerizing the mixing medium. Paper tapes impregnated withture on the joint to form a continuous welded styrene are wound aroundthe joint in succesconnection with the impregnated paper insula-L/sivelayers as indicated at 6, until the diameter tion of the cable. of theinsulation for the full length of the joint Preferably paper or liketape impregnated with reaches that of the external diameter of the thesaid styrene or styrene mixture is first aplead sheath. The appliedinsulation is secured 20 plied to the joint. at each end by cotton.string impregnated with The invention further provides a process ofstyrene andan over-all binding of metallized pajointing high tensioncables wherein after the per l' is wound over the insulation of thejoint, conductor has been joined and a lead or like care being taken toensure that good contact is :5 sleeve has been fitted over the joint,styrene or a made between the lead sheaths and the metal- 25 mixture ofstyrene and chlorinated aromatic hylized paper, for example, by thebinding indicated drocarbon is iilled into the sleeve preferably at 8,8. under pressure, and heat is applied to polymerize The lead sleeve 3is then slipped into position the styrene in the sleeve to form a solidmass of over the joint and plumbed to the cables sheaths :lo insulatingmaterial therein. 2, 2 as indicated at 9, 9. This sleeve is pro- 30 Theinvention also provides an improved vided with filling plugs I0, illthrough which the method of constructing barrier joints in oilimevacuation and impregnation with styrene are pregnated cables byblocking the channels which y effected as will be hereinafter described.

may exist between the joint sleeve and the In making a three core cablejoint as shown in styrene insulation and in the copper strand as Figs; 2and 3, the procedure for each individual 35 will be hereinafterdescribed. core is similar to that already described with ref- The aboveand other features of the invention erence characters to Fig. l, and thesame referwill be described with reference to the accomences hereinrefer to similar parts. In this case, panying drawings, in whichhowever, the outer binding of metallized paper l 40 Fig. 1 is alongitudinal section of a single core on each of the cores makeselectrical connection 40 cable joint constructed in accordance with thiswith the outer metallized paper layers of the invention; cores indicatedat Il, Il', so that the diameter Fig. 2 is a longitudinal section of athree-core of the completed joint is substantially the same cable jointaccording to the invention; asfthat of the external diameter of the leadFig. 3 is a cross-section on the line B-B of sheath 2, 2. 45 Fig. 2; Aswill be seen, this joint is provided with two Fig. 4 is a diagramshowing the method of lead sleeves, the inner one 3A being providedfilling the joint, and with filling plugs I0, lil', as described withrefer- Fig. 5 is a diagram showing one arrangement ence to theconstruction in Fig. 1, but in this for heating the joint. case thesleeve is constructed of thinner metal 50 In making a single core jointaccording to the and it is collapsed around the insulated cableinvention as shown in Fig. 1, the cable ends are cores as shown incross-section in Fig. 3. This prepared for jointing in the usual manner,the can be conveniently effected by applying vacuum paper insulationbeing removed to form a taper to one ofthe filling plugs whilst theother reat the respective cable ends as shown at l, I', mains closed,whereby the sleeve collapses in- 65 wards to conform to the coresection. If necessary, the sleeve may be further dressed down by hand sothat as inuch space as possible between the cores inside the sleeve iseliminated. After the lling and poiymerizing process has been applied tothe joint as will be hereinafter described. the outer sleeve plumbed tothe cable sheaths as indicated at i3, i3'. If desired tivo copper wipedjoints. After this test, the copper tubes may be connected respectivelyto a reservoir containing suitable nlling oil and a vacuum pump wherebythe sleeve may be completely illed with insulating oil alter which thenipples are removed and the as indicated at i4, i4'. The joint is nowcompleted except for the ixing of the outer protection cover andnecessary ing requirements.

Referring new to the actual method of lling and polymerizing jointsaccording to this inven- Figs. 4 and 5, the method of lling beingsubstantially the same as that commonly employed for lling oilimpregnated joints. with the exception that styrene instead of oil. Aswill be seen from Fig. 4, lling pipes 2Q, 20 are screwed into the llingplugs provided on the sleeve of the joint. Pipe 2D is connected to avacuum pump vhereas pipe 2D is connected through a feed control tap 2|to the compound reservoir 22. Suitable glass sight tubes 23, 23 areincluded in the pipe connections by means of rubber connecting sleevesas shown. Pumping proceeds for a short time after which in Fig. 5 arethen ixed to the pipes and these in turn are filled up With styrenecompound.

After completion of the filling, the heating apparatus which may be ofany suitable type is applied to the joint. As shown in Fig. 5, theheatperiod for the styrene to acquire a denitely resinous consistency.This indicates that the degree of polymerization is adequate. Athermometer` as indicated at 28 may be provided to keep a check on thetemperature. During the heating period, the two funnels 24, 24' shouldbe topped or armour as may be required.

During the heating process the styrene is polymerized to polystyrenewith the result that at the welded into the tapered cable insulation sothat the tapered surface no longer exists and the path of low resistanceto electrical Ilashover or breakdown is eliminated.

A joint so constructed will constitute a baroverall nish to theinsulation a which resists further leakage. This method may be used inconjunction with (a).

(c) It has been discovered that under certain conditions the styreneduring polymerization adcable insulation and the new joint insulation.It any oil which may ilow into the joint during processing therebyproducing a more flexible nal production than the pure polystyrene.

chlorinated aromatic hydrocarbon arez- (a) Chlorinated naphthalene.

(b) Chlorinated diphenyl.

Styrene is chemically known as phenylethylene or vinylbenzene. FormulaC6Hs-CH:CHz. The following is one method for the preparation cfstyrenez- The dehydration of beta. phenyl ethyl alcohol comprises thesubtraction of 1 molecule of water per molecule of alcohol.

With regard to heating, investigation has shown that polymerizationproceeds so rapidly during the rst 3 or 4 hours at 120 C. that theliquid thickens during this time to a point outside the range ofviscometry, i. e. it becomes plastic.

C.) polymerization thereafter proceeds at a fairly rapid rate. Conductorheating u metallized paper As previously described the tapered cadue tocarrying of current, and electrical stress, due to application ofvoltage to the cable both aid polymerization so that if cables are putinto service before polymerization of the joints is complete the jointwill continue to polymerize and thereby automatically be strengthened.

The saving effected in dimensions over the smallest known equivalentjoints is of the following order z-Diameter--approximateiy 3/4' -1length-approximately 10 14' It will be understood that the scope of theinvention is not limited to the precise detailsl given herein. Moreover,although styrene is the only material at present known to givesatisfaction it ispossible that other aromatic mono-olennes may be foundto be suitable. Furthermore joints made in accordance with theprinciples of this invention must not be confused with proposals whichhave been made from time to time to use materials like Bakelite varnishas a nlling medium in cable joints, Bakelite varnish being a varnishwhich employs as a base "Bakelite", a phenol condensation product. Insuch cases the material is changed from the liquid to the solid state byboiling off the volatile constituents which inevitably results in theformation of blow holes; nor can a weld with the oily surface of thecable papers be effected, for which reasons these prior processes havenever met with any success.

What is claimed is:-

1. A method of jointing oil impregnated paper insulated high tensioncables which comprises insulating the joint with a mixture of styreneand chlorinated aromatic hydrocarbon and thereafter polymerizing themixture on the joint to form a homogeneous solid insulation with theimpregnated paper insulation of the cable.

2. 'I'he method of jointing oil impregnated paper insulated high tensioncables, comprising tapering in known manner the paper insulation at theends of the cable cores to be jointed, treating the tapered paperinsulation with a solution of chlorinated aromatic hydrocarbon, applyingto the jointed cores paper tapes impregnated with styrene and extendingsuch tapes over said tapered insulation, and subsequently applyingliquid styrene to the joint and polymerizing it on the joint to form asolid insulation thereat.

3. The method of -jointing multi-core high tension cables whichcomprises jointing and insulating the individual cores thereof andclosing the jointed cores in a sleeve and uniting the sleeve in knownmanner with the cover of the cables being jointed, illling the sleevewith liquid styrene, collapsing the sleeve about the cores and merizingsaid styrene prises the cables to be joined, uniting the conductors" tomake an electrical connection, treating the exposed paper insulation atthe ends of the cables with a mixture of liquid styrene and chlorinatedaromatic hydrocarbon, thereafter wrapping the united exposed conductorswith porous insulating material impregnated with liquid styrene, en-

casing the joint, evacuating and then nlling said casing with liquidstyrene, and applying heat to the joint to poiymerize the liquid styreneand thus form a solid insulation about the joint.

5. 'Ihe method of forming a barrier joint between sections of oilimpregnated paper insulated high tension electric cables which includesthe stepsv of lexposing the core conductors and paper insulation,forming a solid joint between the core conductors, wrapping the jointedcore conductors with paper tape, encasing the joint, filling the casingwith liquid styrene about the paper wrapped joint. and thereafterpolymerizing the styrene at the joint to form a solid insulationintegral with the paper insulation oi.' the cable.

6. A method of jointing oil impregnated paper insulated electric cableswhich includes the steps of exposing the core conductors and paperinsulation of the cables, joining the core conductors, wiping theexposed paper insulation with a common solvent for oil and styrene forremoving the oil from the surface thereof, some of said common solventremaining in said insulation, covering the jointed core conductors withporous material, encasing the joint, filling the casing with liquidstyrene about the porous material covered joint, and thereafterpolymerizing the styrene at the joint within the casing to form a solidinsulation integral with said porous material and with the paperinsulation of the cable.

'1. The method of forming a barrier in an oil impregnated paperinsulated cable having the insulation removed from a portion thereof anda length of the conductor exposed, which comprises wrappinx the exposedconductor with paper tape, encssing the wrapped conductor. nlling thecasing with liquid styrene about the paper wrapped conductor, andthereafter polyto form a solid insulation integral with the paperinsulation of the cable.

JOHN KRAUSS WEBB.

